Editor’s Note: The recent spate of cycling traffic fatalities has been startling. The Bike Fed will be there to make sure that these tragedies are not forgotten. Where drivers are at fault, we will push for tough prosecutions or new laws, where necessary. But it’s also important to keep in mind that cycling is becoming much safer across broad populations. So we asked a national expert on that subject, Prof. Robert Schneider of the University of Wisconsin-Milwaukee, to pen this piece sharing his research into cycling safety in the U.S. We hope you find his work encouraging.

Mirroring a national trend, the number of bicycle fatalities in Wisconsin has increased in the last two years. After averaging approximately 10 bicycle fatalities per year over the last decade, 15 bicyclists were killed in Wisconsin in 2015, and there are more bicycle fatalities in 2016 than this time last year. One bicycle fatality—or any type of traffic fatality—is too many, as it represents the loss of a family member, a friend, and a member of our community. Clearly, we need to design safe roadways and provide high-quality bicycle facilities, educate drivers and bicyclists about safe behaviors, and enforce traffic laws.

Avoiding the implication that riding a bicycle on public roads is more risky than it is represents one of the challenges in promoting safety. Examining and detailing crashes and fatalities in the interest of promoting better bicycling has the potential to cause people to ride less.

Discouraging riding is a problem because research shows that higher levels of bicycling are generally associated with lower risk for any individual bicyclist: “safety in numbers.” Following this logic, reducing the number of riders is likely to increase the risk to those who do ride. Therefore, bicycle infrastructure, education, and enforcement strategies to improve safety should be complemented by more encouragement to ride.

Comparing crash rates over different time periods further validates safety in numbers.

For example, bicycle trips in the United States increased by 19 percent between 2001 and 2009, but the crash rate decreased from 0.209 fatal crashes per million bicycle trips to 0.164 fatal bicycle crashes per million bicycle trips. We also found evidence of safety in numbers when analyzing the Wisconsin crash data from 2006 to 2013.

Like other statistical relationships, there are exceptions to safety in numbers. For example, the steep increase in annual bicycle fatalities in Wisconsin in 2015 and 2016 may actually be an example of increasing bicycle activity and an increased fatality rate. However, we do not know how much bicycling occurred in Wisconsin during these two years. Even if these two years do not follow the overall trend in safety in numbers, the large body of research on this topic suggests that safety in numbers should generally hold in the long run.

In addition, more research is needed to understand why we see safety in numbers.

One explanation is that drivers are more aware of bicyclists in areas with more bicyclists and therefore drive more carefully around them. For example, if a driver sees you bicycling, that driver may be less likely to look down at his or her phone when approaching the next bicyclist. Another explanation is that safety in numbers is due to infrastructure, education, and enforcement actions that first create safer conditions so that people then choose to ride more. Both explanations likely contribute to safety in numbers. Regardless of which explanation is more prominent, the safety in numbers relationship is found in study after study. And if more bicycling can help increase driver awareness of bicyclists to any degree, encouraging bicycling can be a great way to complement other bicycle safety strategies.

Data Notes:

Overall bicycle crash, injury, and fatality numbers are available from a variety of sources:

These sources show that there has been an increase in the number of bicycle fatalities in the United States over the last five years or so and in Wisconsin for the last two years. However, those statistics do not indicate whether or not bicycling is becoming relatively safer or not. This is because the raw numbers are affected by the overall amount of bicycling activity within a given area over a given time period. The safety of any individual bicyclist is best represented by a crash or fatality rate (e.g., crashes per million trips; fatalities per million trips; crashes per million minutes bicycled). The safety in numbers relationship has been identified by examining crash and fatality rates.

About Dave Cieslewicz, Director Emeritus

Dave Cieslewicz served two terms as mayor of Madison where he set the city on a path for Platinum status as one of the best biking cities in North America. Before that he started his own nonprofit, 1000 Friends of Wisconsin, which focuses on land use and transportation policy. He has been an adjunct professor at the UW Madison's Department of Urban and Regional Planning where he teaches a class called Bikes, Pedestrians and Cities. He pronounces his name chess LEV ich, but nobody else does.

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I would be curious to see how the serious injury rate varies with number of bicyclists. In some ways, a serious injury is worse than a fatality because in addition to losing the person’s ability to contribute to society, there are extremely high medical and rehabilitation costs that can amount to several million dollars.

Good question about serious injuries, Gregory. Our analysis of Wisconsin bicycle crash data from 2006 to 2013 included both serious and fatal injuries (most of which were serious rather than fatal). We compared these injury numbers to bicycle activity levels (measured by bicycle commuting to work–not a perfect measure but the best available for the time period). See Table 4 on p. 8 of the document at http://wisconsindot.gov/Documents/safety/education/crash-data/bikeped-crash-2011-2013-exec.pdf. In addition, two of the analyses in Jacobsen’s 2003 paper–a comparison of 68 California cities and a comparison of 47 Danish towns–examined all injury levels (including serious injuries). Both our Wisconsin analysis and Jacobsen’s study suggest that “safety in numbers” for bicyclists is likely to hold for serious injuries as well as for fatalities. It would be interesting to see more studies focusing specifically on serious injuries.